1. Field of the Invention
The present invention relates to a display that provides information regarding a projectile trajectory so that a user is informed whether or not there is a clear shot. The present invention also relates to devices such as handheld rangefinders that would comprise such a display and the methods for indicating a clear shot, some of which may be implemented as computer programs.
2. Description of Prior Art
Bows and arrows, spears, crossbows, guns, and artillery have been used for sport, hunting, and military.
An arrow is typically shot using the arms to pull back the bow string, and to aim and sight by holding the bow and arrow next to the archer's eye. More recently bow sights have been added to all types of bows. Typically a bow sight comprises a plurality of pins that may be adjusted by the archer for aiming at targets at different distances. Some bow sights have a single adjustable pin that is moved to the match the distance to the target.
FIG. 1 shows an archer 100 with a compound bow 102 with a bow sight 110, and an arrow 104.
FIG. 2 shows an example of a bow sight 110 with pins adjusted for twenty yards, forty yards, and sixty yards, namely a twenty-yard pin 220, a forty-yard pin 240, and a sixty-yard pin 260, respectively.
Balls and/or bullets are typically shot from a gun using the arms to aim and sight by aligning the gun sights or gun scope reticle with the target.
Artillery balls and shells are typically shot by adjusting the aim mechanically.
Arrows, spears, balls, bullets, and shells when fired follow a ballistic trajectory. Such projectiles, which are not self-propelled, move through air according to a generally parabolic (ballistic) curve due primarily to the effects of gravity and air drag. The vertex form for a parabolic equation is y=a(x−h)2+k, where the vertex is the point (h, k) and a negative a (−a) is a maximum. The standard form of the parabolic equation is y=ax2+bx+c, where h=−b/(2a) and k=c−b2/(4a).
Rifle and bow scopes conventionally have been fitted with reticles of different forms. Some have horizontal and vertical cross hairs. Others reticles such as Mil Dot add evenly spaced dots for elevation and windage along the cross hairs. United States Design Patent D522,030, issued on May 30, 2006, shows a SR reticle and graticle design for a scope. Various reticles, such as Multi Aim Point (MAP) and Dot are provided, for example, by Hawke Optics (http://hawkeoptics.com). These reticles are fixed in that the display does not change based on range information. Also, these reticles indicate the approximate hold-over position in that they are positioned under the center of the scope, i.e. below where the cross hairs intersect. They are not necessarily precise, for example, for a specific bow and archer, but are approximation for the general case.
Hunters and other firearm and bow users commonly utilize handheld rangefinders (see device 10 in FIG. 1) to determine ranges to targets. Generally, handheld rangefinders utilize lasers to acquire ranges for display to a hunter. Utilizing the displayed ranges, the hunter makes sighting corrections to facilitate accurate shooting.
For example, U.S. Pat. No. 7,658,031, issued Feb. 9, 2010, discloses handheld rangefinder technology from Bushnell, Inc, and is hereby included by reference. As shown in FIG. 3, a handheld rangefinder device 10 generally includes a range sensor 12 operable to determine a first range to a target, a tilt sensor 14 operable to determine an angle to the target relative to the device 10, and a computing element 16, coupled with the range sensor 12 and the tilt sensor 14, operable to determine a hold over value based on the first range and the determined angle. The range information is displayed on a display 30. A housing 20 contains the elements of the device 10. Bushnell Angle Range Compensation (ARC) rangefinders show the first linear range to the target and also show an angle and a second range, which represents the true horizontal distance to the target. Handheld rangefinders, telescope sights, and other optical devices typically comprise a laser range sensor and an inclinometer.
The range information is superimposed over the image that is seen through the optics. For example, United States Design Patent D453,301, issued Feb. 5, 2002, shows an example of a design for a display for a Bushnell rangefinder, and is hereby included by reference. FIG. 4 shows an exemplary display 30 appearing in a handheld rangefinder device 10.
The ideal hunting target is shown in FIG. 5 where the target T, in this example, a deer, is in an open, level field with no obstacles. In practice, the target is often not at the same level and there are numerous obstacles between the shooter and the target. FIG. 6 shows a more realistic situation. In the field there may be obstacles such as tree branches, bushes, and other wildlife which are not the target and which may interfere with the trajectory of the projectile.
With convention rangefinder and a bow sight there is no correlation between the display of the rangefinder and the user's individual bow sight. To make an effective shot requires several steps. First the user operates the rangefinder to range the target. Second, the user raises the bow and uses the bow sight pins to visualize the shooting area. Third, the user lowers the bow and raises the rangefinder again to find the range to each object that may be a potential obstacle. Fourth, the user lowers the rangefinder and raises the bow to make the shot. All of the movement and time taken during these steps will likely be noticed by the target and allow the target an opportunity to move resulting in having to repeat the process or miss the shot altogether.
What is needed is an improved rangefinder with a display that provides information regarding a projectile trajectory so that a user is informed whether or not there is a clear shot. Further, the improved rangefinder dynamically indicates positions along the trajectory based on ranges accurately determined by the rangefinder, such that the user is informed about the distance to specific obstacles and whether or not the obstacles would interfere with the trajectory of the projectile. Further, for bow use, the indicators on the display need to correspond to the bow sight pins.